Renew process implementation for reactor bottom head

Abstract

A surface conditioning scheduling process is used to mitigate susceptibility to crack initiation or crack growth in a boiling water nuclear reactor using a plurality of working crews. A plurality of working zones are defined in an annulus region of a reactor vessel flange, and a plurality working zones are defined in a core region of the reactor vessel. One of the working crews is positioned in each of the annulus region working zones, and one of the working crews is positioned in each of the core region working zones. The working crews perform surface conditioning in areas of the reactor vessel accessible from their respective working zones such that the surface conditioning process can be completed in no more than thirty days.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to mitigating crack initiation or growth of small cracks in a nuclear reactor vessel and, more particularly, to an implementation / scheduling process for mechanical surface conditioning of metals to mitigate crack initiation or growth. Delivery of other processes to the component surfaces is also contemplated.[0002]The welds in the bottom head region of a reactor vessel in a boiling water nuclear reactor are susceptible to cracking. Repair of such cracking requires complex and expensive processes. A known ‘ReNew™ process’ has been used to mitigate susceptibility to crack initiation or growth of small cracks due to tensile surface stresses, stress corrosion initiation and fatigue crack initiation using a mechanical surface conditioning of metals. These stresses can be found in the welds and heat affected zones of the reactor bottom head. The quantity of welds in the vessel head region, however, is very large, and it is typ...

AI Technical Summary

Benefits of technology

The patent describes a process to prevent cracks in a boiling water nuclear reactor by conditioning the surface of the reactor vessel using multiple working crews. The process involves defining working zones in both the annulus region of the reactor vessel flange and the core region of the reactor vessel. Each working crew is then assigned to a specific working zone and performs surface conditioning in their respective zones for no more than thirty days. This process reduces the risk of crack initiation or growth due to surface stresses and ensures safe and efficient operation of the boiling water nuclear reactor.

Problems solved by technology

The welds in the bottom head region of a reactor vessel in a boiling water nuclear reactor are susceptible to cracking.

Repair of such cracking requires complex and expensive processes.

The quantity of welds in the vessel head region, however, is very large, and it is typically very time consuming to mitigate all welds.

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